Method for dissolving gases in liquids



Nov. 1, 1966 1. 3uca- 3r-:\\|E.ER ;.ER 3,282,571

METHOD FOR DISSOLVING GASES IN LIQUIDS Filed March 30, 1964 Fig.

.7n ven for United States Patent O 3,282,571 METHGD FOR DISSOLVING GASESIN LIQUIDS Johann Gnggenberger, Munich, Germany, assignor to Holstein d;Kappert Maschinenfabrik Phonix G.m.b.H., Dortmund, Germany Filed Mar.30, 1964, Ser. No. 355,649 Claims priority, application Germany, Mar.28, 1963, H 48,668 3 Claims. (Cl. 261-1) The present invention relatesto a method for dissolving gases in liquid and is particularly concernedwith a method for producing gas impregnated beverages such as carbonatedsoft drinks, beer and the like.

It is an object of the present invention to provide a method for thequick dissolution of gas upon introduction ofthe same into a liquid.

Ot-her objects and advantages of the present invention will becomeapparent from a further reading of the description and of the appendedclaims.

With the above and other objects in view, the present inventioncontemplates a method of dissolving a gas in a liquid comprising thesteps of subjecting a liquid to a predetermined degree ofsuperatmospheric pressure, introducing gas into the liquid while thetime is under the predetermined pressure in an amount such that thepredetermined pressure exceeds the saturation pressure required formaintaining the gas in solution, and subjecting the thus formed mixtureof gas and liquid to vibrations of sonic character having an amplitudeso chosen that the pressure drop corresponding to the negative portionof the amplitude is smaller than the difference between thepredetermined pressure and the saturation pressure.

Thus, the present invention includes a method for dissolving gases inliquids, particularly for producing impregnated beverage such as softdrinks, i.e. carbon dioxide impregnated aqueous liquids for humanconsumption, and the like, according to which the mixture of liquid andgas bubbles formed by introducing gas into the liquid is subjected tosonic vibrations, generally, but not necessarily, ultrasonic vibrations,while the mixture of gas and liquid is maintained at an elevatedpressure which is at least as lhigh as the sum ofthe saturation pressureof the gas of the mixture in lthe liquid plus the .pressure dropcorresponding to the negative portion of the amplitudeof the sonic orultrasonic vibrations.

In other words, the liquid-gas mixture, while being subjected to thesonic or ultrasonic vibrations, will always be under a pressure which isat least as high and preferably somewhat higher than the saturationpressure of the gas in the liquid. This saturation pressure will willdepend on the type of liquid, the type of gas, the temperature and theamount of gas per unit of liquid which is introduced into the latter andit is well within the skill of the art to determine this saturationpressure as well as the pressure drop corresponding to the negativeportion ofthe amplitude of the vibrations of sonic character for anygiven operating conditions.

The essential elements of the device or arrangement for dissolving gasin a liquid in accordance with the present method are a conduit leadingfrom a source of liquid, for instance, a storage tank to another storagetank in which the iinal product is maintained under the above describedpredetermined elevated pressure.

A pressure pump or the like is arranged in the conduit for the purposeof subjecting the liquid passing therethrough to a pressure which issuiiciently higher than the pressure required for maintaining thedesired amount of gas in solution in the liquid so that when the liquidis subjected to vibrations of sonic character, the pressure dropcorresponding to the negative portion of the amplitude of suchvibrations will not suice to reduce the Patented Nov. l, 1966 pressureof the liquid to below the saturation pressure required for maintainingthe desired amount of gas in solution in the liquid.

The desired proportion of gas is then introduced in-to the thuspressurized liquid and will be partially dissolved therein and willpartially form gas bubbles in the liquid.

The thus formed mixture of gas and liquid is then subjected tovibrations of sonic character which will serve the purpose of causingdissolution of the gas bubbles in the liquid provided that, inaccordance with the present invention, at no time the pressure of theliquid is lowered or drops below the saturation pressure required forholding the desired amount of gas in solution in the liquid.

Vibrations of sonic character cause alternately an increase and areduction in the pressure of the liquid which is subjected to suchvibrations and it is essential according to the present invention thatduring the periods when the vibrations cause a decrease in the pressureof the liquid, nevertheless the residual pressure will be at least ashigh and preferably somewhat higher than the saturation pressurerequired for maintaining the entire amount of gas in solution in theliquid.

In the past, ultrasonic vibrations have been used for degassing liquidsand it has been found that the speed of withdrawal of dissolved gas fromliquids can be greatly increased by subjecting such gas containingliquids to ultrasonic vibrations. However, in such cases, at leastduring the pressure drop corresponding to the negative portion oramplitude of the ultrasonic vibrations, the residual pressure of theliquid will fall below the saturation pressure required for holding thegas dissolved in the gas preferably below atmospheric pressure.

In contrast thereto, according to the present invention, the pressure ofthe liquid-gas mixture will be at all times higher or at least as highas such saturation pressure and under these conditions which are to bemaintained according to the present invention, it has been found that,surprisingly, vibrations of sonic character greatly facilitate thedissolution of the gas in the liquid.

Ultrasonic vibrations cause or generate pressure waves in liquidsexposed thereto, which pressure Waves `comprise a positive component(pressure increase) and a negative component (decrease in pressure downto the tension stress or cohesion pressure between the molecules of theliquid). By applying a counterpressure against the negative amplitude ofthe sonic or ultrasonic vibrations, i.e. by increasing the outerpressure above the saturation pressure of the gas in the liquid, thedegassing of the gas-containing liquid is sl-owed down. Upon furtherincreasing such counterpressure, i.e. by maintaining a pressure equal toor greater than the sum total of the saturation pressure and thepressure drop corresponding to the negative portion of the amplitude ofthe sonic or ultrasonic wave, this effect, namely the degassing of theliquid, is reversed and the speed of dissolution of gas in the liquid isgreatly increased. The total pressure, or the counterpressure which isto be applied during the sonic or ultrasonic treatment of the liquid-gasmixture will depend on the intensity of the ultrasonic or sonic wavesand must be sufficiently high so that even during the negative componentor portion of the amplitude of the vibrations, the total pressure towhich the liquid-gas mixture is subjected will be greater than thesaturation pressure required for maintaining the gas in solution in theliquid.

Experiments have shown that in many cases this result can be achieved bymaintaining the g-as-liquid mixture while the same is subjected to sonicor ultrasonic vibrations under an absolute pressure lof between aboutthree and six atmospheres.

Ultrasonic vibrations produced in the liquid do not dritter basicallyfrom vibrations which may be produced with Iaudible wave lengths. It istherefore also possible to achieve the acceleration of the dissolutionof gas in the liquid with vibrations within the audible range, forinstance, |by means of a 50 Hz. vibrator,

An optimum effect is achieved when the size of the gas bubbles is suchthat the resonant frequency of the body of gas contained therein is4substantially equal to the frequency of the vibrations of soniccharacter applied to the liquid.

The novel features which are considered as characteristie for theinvention are set forth 1in particular in the appended claims. Theinvention itself, however, both as to its construction and its method ofoperation, together with additional objects :and 'advantages thereof,will be best understood from the following description of specificembodiments when read in connection with the accompanying drawings, inwhich:

FIG. 1 is a schematic illustration of the pressure conditions in theliquid-gas mixture while the same is subjected to sonic or ultrasonicvibrations in accordance with the present invention, and

FIG. 2 is a schematic elevational view of an arrangement for dissolvinggas in a liquid in accordance with the present invention, for instance,for dissolving carbon dioxide in beverages, ie. aqueous liquids.

Referring now to FIG. l, the saturation pressure, i.e. the pressure atwhich the desired amount of gas will remain dissolved in the liquid, isindicated by the line Ps. The liquid, however, is subjected prior tointroduction of the gas, and of course also prior tot the subjecting ofthe liquid-gas mixture to vibrations of sonic character, to the higherpressure Pg so that when the liquid is then subjected to the elfect ofthe sonic yor ultrasonic vibrations S, the minimum pressure will alwaysbe somewhat higher than the saturation pressure Ps.

As illustra-ted in FIG. 2, the liquid, such ras Water or an aqueousliquid including for instance sugar and flavoring agent, is withdrawnfrom a container 1 and passes in the indicated sequence through apressure pump 2, a gasintroducing device which includes a nozzlearrangement 3 and a gas conduit 3a for introducing a gas into the liquidrin the form of finely sub-divided bubbles, then in contact with aconventional sonic vibrations gene-rating device 4 into pressurecontainer 5 and from there through conduit 6 to a filling station, forinstance, a bottle-filling apparatus (not shown).

As described above, gas bubbles will be introduced at 3 into the liquidwhich is under a pressure which is higher than the pressure required formaintaining the amount of gas which has been introduced in solution, anddissolution of the thus introduced gas is accelerated by subjecting theliquid-gas mixture lto the sonic or ultrasonic vibrasonic vibrationsgenerated Iat 4, under the pressure conditions discussed further above.

It will be understood that each of the elements described above, or twoor more together, may also iind a useful application in other types ofdevices for dissolving a gas in ia liquid diering from the typesdescribed above.

While the invention has been illustrated and described as embodied in anarrangement primarily intended for carbonating beverages, it is notintended to be limited i to the details shown, since variousmodilications and structural changes may be made without departing inany way from the spirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist ofthe present invention that others can by applying current knowledgereadily adapt it for varilous yapplications without omitting featuresthat, from the ystandpoint of prior art, fairly constitute essentialcharacteristics of the generic or specic aspects of this invention and,therefore, such adaptations should and are intended to be comprehendedwithin the meaning and range of equivalence of the following claims.

What is claimed as new and desired to be secured by Letters Patent is:

1. Method of dissolving a gas in a liquid comprising the steps ofsubjecting a liquid to a predetermined degree of supenatmosphericpressure; introducing gas into said liquid while the same is under saidpredetermined pressure in an amount such that said predeterminedpressure exceeds the saturation pressure required for maintaining saidgas in solution; and subjecting the thus formed mixture of gas andliquid to vibrations of sonic character having an amplitude so chosenthat the pressure drop corresponding to the negative portion of saidamplitude is smaller than the difference between said predeterminedpressure and said saturation pressure.

2. Method of dissolving a gas in a liquid comprising the steps ofsubjecting a liquid to a predetermined degree of superatmosphericpressure; introducing gas into said liquid While the same is under saidpredetermined pressure in an amount such that said predeterminedpressure exceeds the saturation pressure required for maintaining saidgas in solution; 1and subiecting the thus formed mixture of gas andliquid to ultrasonic vibrations having an amplitude so chosen that thepressure drop corresponding to the negative portion of said amplitude issmaller than the difference between said predetermined pressure and saidsaturation pressure.

3. Method of dissolving a gas in a liquid comprising the steps ofsubjecting :an aqueous liquid to a predetermined degree o-fsuperatmospheric pressure; introducing carbon dioxide gas into lsaidaqueous liquid while the same is under said predetermined pressure in anamount such that said determined pressure exceeds the saturationpressure required for maintaining said carbon dioxide gas in solution;and subjecting the thus formed mixture of carbon dioxide gas and aqueousliquid to vibrations of sonic character lhaving an amplitude so chosenthat the pressure drop corresponding to the negative portion of saidamplitude is smaller than the diierence between said predeterminedpressure and said saturation pressure.

References Cited by the Examiner UNITED STATES PATENTS 1,768,158 6/1930Shields.

Y FOREIGN PATENTS 942,608 9/1948 France.

HARRY B. THORNTON, Primary Examiner.

RONALD R. WEAVER, Examiner,

1. METHOD OF DISSOLVING A GAS IN A LIQUID COMPRISING THE STEPS OFSUBJECTING A LIQUID TO A PREDETERMINED DEGREE OF SUPERATMOSPHERICPRESSURE; INTRODUCING GAS INTO SAID LIQUID WHILE THE SAME IS UNDER SAIDPREDETERMINED PRESSURE IN AN AMOUNT SUCH THAT SAID PREDETERMINEDPRESSURE EXCEEDS THE SATURATION PRESSURE REQUIRED FOR MAINTAINING SAIDGAS IN SOLUTION; AND SUBJECTING THE THUS FORMED MIXTURE OF GAS ANDLIQUID TO VIBRATIONS OF SONIC CHARACTER HAVING AN AMPLITUDE SO CHOSENTHAT THE PRESSURE DROP CORRESPONDING TO THE NEGATIVE PORTION OF SAIDAMPLITUDE IS SMALLER THAN THE DIFFERENCE BETWEEN SAID PREDETERMINEDPRESSURE AND SAID SATURATION PRESSURE.